The present invention relates to a method for reactive preparation of a shaped body of a refractory or other functional inorganic compound of a metal. More particularly, the invention relates to a method for the preparation of a shaped body of an inorganic compound of a metal in a thinly extended or plate-like form by the in situ reaction in a powder compact of reactant components under compression. The invention also relates to a method for forming a coating layer of a refractory or other functional inorganic material on the surface of a substrate by the in situ reaction in the coating layer of a power mixture of reactant components on the substrate surface.
In the prior art, shaped bodies of a refractory or other functional inorganic compound of a metal, such as carbides, borides, silicides, sulfides, nitrides and oxides of a metal, e.g., aluminum, titanium, zirconium, magnesium, molybdenum, etc., are prepared usually in the so-called power metallurgical method in which the respective compound is manufactured in a fine powdery form which is shaped, for example, by compression molding into a powder compact or green body followed by prolonged heating to effect sintering of the green body at a high temperature under normal pressure or under high pressure using a hot press or hot isostatic press. This conventional method is disadvantageous due to the lengthy sintering process taking a long time and the low versatility of the method when a sintered body of a complicated form is desired.
As a method for forming a coating layer of an inorganic compound on the surface of a substrate such as ceramics, there are known several methods including the plasma spray method, CVD method, PVD method and the like. These methods are advantageously utilized when the desired coating layer has a relatively small thickness but the method is hardly practical when a coating layer having a relatively large thickness is desired because the rate of deposition of the coating layer is usually low.
Recently, a method of reactive sintering is disclosed in Japanese Patent Kokai No. 60-246270 and Japanese Patent Kohyo No. 57-500289 according to which a shaped body of a ceramic such as titanium boride is prepared by igniting a powder mixture of a metallic element, e.g., titanium, and a non-metallic element, e.g., boron, so that the exothermic reaction between the elements is propagated to the whole mass of the powder mixture and the powder mixture is converted in situ into a sintered body of the compound of the metallic and non-metallic elements by the heat of reaction without supply of external heat. This method, however, is not quite satisfactory in respect of the relatively low conversion of the starting powdery reactants into the desired compound so that the thus obtained sintered body cannot have fully reproducible properties.